The test of President Obama's seriousness about addressing climate change is not his pending decision on the much-debated Keystone XL pipeline. It's whether he effectively consigns coal-fired power plants -- one of the biggest sources of carbon emissions -- to the ashcan of history.
Since his re-election, Obama has signaled a new focus on climate change. "Some may still deny the overwhelming judgment of science, but none can avoid the devastating impact of raging fires, and crippling drought, and more powerful storms," he said in an inaugural address that devoted eight sentences to the issue, more than he spent on any other item on his policy agenda.
The strong words from Obama were a welcome surprise. Few doubted that the president understood and accepted the scientific consensus about humankind's impact on the climate. His dramatic toughening of automobile fuel-economy standards, announced last year, was a major step that will eventually produce great benefits. But it has been unclear whether he is prepared to take similarly bold action to mitigate the other big source of atmospheric carbon dioxide: emissions from power plants.
"If Congress won't act soon to protect future generations, I will," Obama vowed in his State of the Union speech. That's what I'd call unequivocal.
As if Obama needed more of an incentive, a new National Oceanic and Atmospheric Administration study published last month in the journal Geophysical Research Letters confirms that temperatures have been rising ever since the Industrial Revolution -- when the burning of fossil fuels dramatically increased -- just as climate scientists have been telling us.
The difference with this study is that it does not rely on direct temperature readings, which climate-change skeptics deride as skewed and unreliable. Nor does it use data from examination of tree rings. Instead, it relies on proxy data from 173 sources such as ice cores, lake and ocean sediments, mineral deposits and historical records of agricultural harvests -- all of which are sensitive to temperature. Plotted on a graph, the upward trend looks just like climate scientists said it would.
Earlier this month, tens of thousands of demonstrators rallied in Washington to urge Obama to reject the Keystone XL pipeline, which would ship crude oil from the Athabasca tar sands in Alberta, Canada, to ports in Texas along the Gulf Coast. Organizers claimed it was the biggest climate protest ever in the United States.
Activists say the process of extracting oil from the tar sands generates more carbon emissions than conventional means of oil recovery. It is true that the pipeline might accelerate exploitation of the tar sands. But the oil is likely to be extracted eventually, regardless of the pipeline decision.
Meanwhile, about 40 percent of U.S. carbon emissions come from power plants, and coal-burning plants produce far more emissions than facilities that use other fuels -- more than twice as much, per unit of electricity generated, than plants burning natural gas, for example.
Low prices for natural gas have caused utilities to switch fuels. Ten years ago, according to the Energy Information Administration, half of the nation's electricity came from coal-fired plants and less than one-fifth from plants burning natural gas. Last year, just 37 percent was generated by coal -- and about 30 percent by natural gas.
Obama has the opportunity to cut carbon emissions by hastening a transition already under way -- without action by the hostile Republican majority in the House or the nervous Democratic majority in the Senate.
The Environmental Protection Agency has the power -- I'd call it a duty -- to issue rules limiting carbon emissions per unit of electricity generated. Tough, science-based rulemaking would give utilities an incentive to switch from coal to gas -- and effectively guarantee that no new coal-fired plants would be built.
Obama has to weigh the political impact on Democratic elected officials in coal-producing states such as West Virginia. But coal-state Democrats are already under pressure because of the shift to natural gas that just happens to be occurring while a Democrat is in the White House. They will have to deal with voters' economic concerns whether Obama acts or not.
Natural gas is not a panacea. The extraction process known as "fracking" -- responsible for the current glut -- raises serious environmental concerns. Ultimately, the only way to halt climate change is to wean the global economy from its dependence on fossil fuels.
But that is a journey of many years. Obama can -- and should -- take us many miles down the road with a stroke of his pen.
Eugene Robinson is a syndicated columnist. Contact him at firstname.lastname@example.org.